Method For Evaluating Component Calibration In Machine Vision Vehicle Wheel Alignment System

1. A method for evaluating a machine vision vehicle wheel alignment measurement system having a plurality of camera components, each of said camera components having a stationary field of view for observing at least one optical target, comprising: disposing a set of optical targets within overlapping regions of the stationary fields of view for said plurality of camera components such that at least one optical target within said set of optical targets is observable by at least two camera components within said plurality of camera components; observing said set of optical targets with said plurality of camera components to acquire a set of images representative of said observed optical targets, said set of images including, for each observed optical target, at least two images acquired from separate camera components within said plurality of camera components; processing said set of images to identity, for each of said observing camera components, data representative of at least one feature associated with said observed optical targets; comparing said identified data from each of said observing camera components to establish at least one representation of performance for at least a single component of the machine vision vehicle wheel alignment measurement system; and wherein said single component may be an established calibration transform, a camera component, an optical target, a calibration fixture, or a vehicle support surface.

2. The method of claim 1 wherein said representation of performance is an identification of at least one defective component associated with the machine vision vehicle wheel alignment measurement system; and wherein said defective component may be an established calibration transform, a camera component, an optical target, a calibration fixture, or a vehicle support structure.

3. The method of claim 1 wherein said representation of performance is an indication of a change in a configuration associated with at least one camera component of the machine vision vehicle wheel alignment measurement system having occurred after a calibration procedure; and wherein said change in configuration is a change in a mounting position of said at least one camera component relative to another camera component, or a change in a configuration of one or more optical elements within said at least one camera component.

4. A method for evaluating a machine vision vehicle wheel alignment measurement system having at least four cameras including, for the left and right sides of a vehicle positioned on a vehicle support surface, a front camera with an associated field of view disposed to view a front wheel of the vehicle, and a rear camera with an associated field of view disposed to view a rear wheel of the vehicle, said rear camera associated field of view and said front camera associated field of view intersecting to define an overlapping region, comprising: providing a fixture having identifiable features; acquiring from said cameras disposed in a selected spatial configuration, a set of images of said identifiable features of said fixture disposed on said vehicle support surface at a plurality of positions within said fields of view, at least one of said plurality of positions disposed within said overlapping regions for said fields of view of said front and rear cameras on each side of the vehicle; processing said set of acquired images to calibrate said plurality of cameras and said vehicle support surface associated with said machine vision wheel alignment measurement system; repeating said step of acquiring to acquire from at least one of said cameras disposed in said selected spatial configuration, a second set of images while said fixture is disposed on said vehicle support surface at a position which is within the overlapping region of the fields of view associated with said front and rear cameras on each side of the vehicle support surface; and processing said second set of acquired images to establish a performance metric for said calibrated machine vision wheel alignment measurement system.

5. The method of claim 4 wherein said second set of images includes images acquired from each of said cameras, and wherein said performance metric is established for said machine vision vehicle wheel alignment measurement system as a whole.

6. The method of claim 4 wherein said performance metric is established for at least one of said cameras.

7. The method of claim 4 wherein said performance metric identifies one of a change in a relative position of one of said cameras relative to another of said cameras, a change associated with a component within at least one of said cameras subsequent to said calibration, or a change associated with at least one of said identifiable features of said calibration fixture.

8. A method for evaluating a machine vision vehicle service system having a plurality of camera components disposed to view each side of a vehicle support surface, comprising: observing a set of optical targets mounted to a fixture with said plurality of camera components to acquire a set of images representative of said observed optical targets, while said fixture is disposed on said vehicle support surface at a position which is within a region of overlapping fields of view associated with said plurality of camera components; processing said set of images to identity at least one of a defective camera component, a defective optical target and a defect associated with said fixture.

9. A method for establishing coordinate transforms between cameras in a machine vision vehicle wheel alignment measurement system, comprising: acquiring, from a first camera in a first position and orientation, at least two images of a portion of a fixture positioned in at least two different locations within the field of view of the first camera, at least one of said images acquired with said fixture positioned on a surface within a region of overlapping fields of view of said first camera and a second camera; acquiring, from said second camera in a second position and orientation, at least two images of said portion of said fixture positioned in at least two different locations within the field of view of the second camera, at least one of said images acquired with said portion of said fixture positioned on said surface within said region of overlapping fields of view of said first camera and said second camera; processing said set of acquired images from each of said cameras to establish a coordinate transform between reference frames of the first camera in said first position and orientation and said second camera in said second position and orientation; wherein said first camera is a front camera having a field of view disposed to view a front wheel of a vehicle disposed on said surface; wherein said second camera is a rear camera having a field of view disposed to view a rear wheel of said vehicle on said same side as said front wheel; and wherein said front and rear cameras are secured in a fixed relationship laterally offset from, and longitudinally in front of, said surface.

10. The method of claim 9 wherein said portion of said fixture includes an optical target.

11. The method of claim 9 further including the steps of: acquiring, from a third camera in a third position and orientation, at least two images of a second portion of said fixture positioned on said surface within a field of view of the third camera, at least one of said images acquired with said second portion of said fixture positioned on said surface within a region of overlapping fields of view of said third camera and a fourth camera; acquiring, from said fourth camera in a fourth position and orientation, at least two images of said second portion of said fixture positioned on said surface within the field of view of the fourth camera, at least one of said images acquired with said second portion of said fixture positioned on said surface within said region of overlapping fields of view of said third camera and said fourth camera; and processing said set of acquired images from said third and fourth cameras to establish a coordinate transform between reference frames of the third and fourth cameras.

12. The method of claim 11 wherein said third camera is a front camera having a field of view disposed to view a front wheel of a vehicle disposed on an associated support surface on an opposite side of said vehicle from said first camera field of view; wherein said fourth camera is a rear camera secured in a fixed relationship with said third camera and having a field of view disposed to view a rear wheel of said vehicle on said same side of said vehicle as said third camera field of view; and wherein said third and fourth cameras are laterally offset from said first and second cameras, and are longitudinally in front of, said surface.

13. The method of claim 11 further including the step of processing said set of images from said first and second cameras together with said set of images from said third and fourth cameras to establish coordinate transforms between associated reference frames of said cameras; and wherein said first and second cameras define a first camera assembly disposed to view one side of a vehicle, while said third and fourth cameras define a second camera assembly disposed to view an opposite side of the vehicle.

14. The method of claim 9 wherein said surface is a vehicle support surface; wherein said fixture is positioned at each of said different locations, on said vehicle support surface during each acquisition step; and further including the step of processing said acquired sets of images to characterize said vehicle support surface.

15. A method for establishing coordinate transforms between multiple cameras in a machine vision vehicle wheel alignment measurement system viewing portions of a vehicle support surface, comprising: providing a fixture adapted to receive a machine vision optical target at each opposing end; disposing said fixture transversely across said vehicle support surface, such that a first optical target disposed at a first opposing end is within the field of view of at least a first camera of the machine vision vehicle wheel alignment measurement system, and a second optical target disposed at a second opposing end is within the field of view of at least a second camera of the machine vision vehicle wheel alignment measurement system, said first and second cameras disposed on opposite sides of a longitudinal centerline of the vehicle support surface; acquiring, from each camera, at least one image of the optical targets within the respective fields of view; displacing the first opposing end of the fixture along the vehicle support surface to a next position which is longitudinally offset from said second end, and acquiring from each camera, at least a second image of the optical targets within the respective fields of view; displacing the second opposing end of the fixture along the vehicle support surface to a subsequent position in the same direction as said displacement of said first end to a next position which is longitudinally offset from said first end, and acquiring from each camera, at least a third image of the optical targets within the respective fields of view; and processing said acquired images to establish at least a coordinate transform between the first and second cameras.

16. The method of claim 15 further including the step of processing said acquired images to characterize the runway surface.

17. The method of claim 15 wherein said machine vision vehicle wheel alignment measurement system is a four-camera system, including a third camera having a field of view partially overlapping the field of view of said first camera, and a fourth camera having a field of view partially overlapping said field of view of said second camera; wherein at least one image from each camera is acquired with the first optical disposed target in the overlapping field of view of the first and third cameras, and with the second optical target in the overlapping field of view of the second and fourth cameras; and wherein said step of processing said images further establishes a coordinate transform between the first and third cameras, and a coordinate transform between the second and fourth cameras.

18. The method of claim 15 further including the step of providing operator guidance for positioning said calibration fixture during said steps of disposing, displacing, and acquiring.

19. The method of claim 15 wherein said set of processing includes establishing a comprehensive characterization data set associated with each of said cameras and said runway from said acquired images.

20. The method of claim 19 wherein said comprehensive characterization data set is optimized to minimize measurement errors associated with each of said cameras.

21. A method for using a machine vision vehicle wheel alignment measurement system having cameras for observing the left and right sides of a vehicle positioned on a vehicle support surface, comprising: providing a fixture having identifiable features; placing said fixture at a first position on said vehicle support surface; acquiring from said cameras, a set of images of said identifiable features of said fixture; repositioning said fixture to at least one longitudinally displaced position on said vehicle support surface; acquiring from said cameras, for each repositioning of said fixture, an additional set of images of said identifiable features of said fixture; and processing said sets of acquired images to generate characterization data for a longitudinal portion of said vehicle support surface over which said longitudinally displaced positions are disposed.

22. The method of claim 21 wherein said characterization data includes height data for a plurality of points on said longitudinal portion of said vehicle support surface.

23. The method of claim 22 wherein said height data represents relative heights between starting and ending positions for each vehicle front tire contact patch during a rolling runout compensation procedure.

24. The method of claim 23 further including the step of comparing said relative heights to an overall runway reference plane to establish a representation of runway quality.

25. The method of claim 21 wherein said characterization data includes altitude data for multiple points along each runway portion of said vehicle support surface.

26. The method of claim 21 wherein said characterization data identifies sloping within said longitudinal portion of the vehicle support surface.

27. The method of claim 21 wherein said characterization data identifies bending along said longitudinal portion of the vehicle support surface.

28. The method of claim 21 wherein said characterization data is utilized to compensate vehicle measurements for runway deviations from level.

29. The method of claim 28 wherein said characterization data is utilized to compensate vehicle measurements for side-to-side deviations in the height of said longitudinal portions of the vehicle support surface on which the left and right wheels of the vehicle are supported.

30. The method of claim 21 further including the step of interpolating characterization data associated with points on said vehicle support surface located between said plurality of positions at which said fixture is disposed.

31. The method of claim 21 wherein said characterization data is utilized to generate a map of the runway surfaces.